This invention relates to golf clubs, and, more particularly, to the material of construction of the golf club shaft and the golf club head.
In the sport of golf, the golfer strikes a golf ball with a golf club. The golf club includes an elongated club shaft which is attached at one end to an enlarged club head and is wrapped at the other end with a gripping material to form a handle. The clubs are divided into several groups, depending upon the function of the club. These groups include the drivers, the irons (including wedges for the present purposes), and the putters.
Because golf has become a highly popular spectator and participant sport, a great deal of development effort has been devoted to golf clubs. Both the design of the clubs and the materials of construction have been improved in recent years. The present invention deals primarily with the materials of construction of golf clubs, and the following discussion will emphasize that subject area.
Until recent years, both the club shaft and the club head have been made primarily of metals such as steel and/or aluminum alloys. Composite-material shafts made of graphite-fiber-reinforced polymeric materials have been introduced, to reduce the weight and increase the material stiffness of the shaft. Heads made of specialty materials such as titanium alloys have been developed, to achieve reduced club head mass and density with high material stiffness so that the club head speed may be increased. The use of such materials also permits the manufacture of a larger-sized club head with the same mass or with redistributed weight and better performance. This brief discussion of new materials used in golf club shafts and heads is by no means exhaustive, and many other materials have been tried in order to achieve particular club behavior based upon various theories of club performance.
There remains a need, however, for further improvements in golf clubs in order to attain high material stiffness, high stiffness-to-weight ratio, and high strength-to-weight ratio. These properties, in turn, lead to higher club head speed and a higher degree of energy transfer from the club to the ball upon impact, thereby permitting any player to perform to the best of his or her ability without being limited by the nature of the golf clubs. The present invention fulfills this need, and further provides related advantages.
The present invention provides a golf club with an improved material of construction. The golf club exploits the unusual elastic properties of the material to provide a high degree of energy transfer from the club to the ball upon impact. The club is also corrosion resistant, wear resistant, and has a low coefficient of club head face friction. The club shaft and head are readily fabricated. For some clubs, the material of construction permits the configuration of the golf club to be modified so as to improve its performance.
In accordance with the invention, a golf club comprises a club shaft and a club head. Either or both of the club shaft and the club head are made at least in part of a bulk-solidifying amorphous metal. If the club shaft is made at least in part of a bulk-solidifying amorphous metal, the entire shaft is desirably made of the bulk-solidifying amorphous material. If the club head is made at least in part of the bulk-solidifying amorphous metal, at least the club head face is made of the bulk-solidifying amorphous material. The club head face may be made thinner and lighter when it is made of the bulk solidifying amorphous metal than when it is made of conventional metals, allowing a desirable redistribution of the weight of the club head toward the periphery of the club head.
A preferred composition for the bulk-solidifying amorphous metal is, in atom percent, from about 45 to about 67 percent total of zirconium plus titanium, from about 10 to about 35 percent beryllium, and from about 10 to about 38 percent total of copper plus nickel, plus incidental impurities, the total of the percentages being 100 atomic percent. Other bulk-solidifying amorphous metals may also be used.
Manufacture of a portion of the golf club from a bulk-solidifying amorphous metal yields surprising and unexpected improvements in club performance. If the club shaft is made of the bulk-solidifying amorphous metal, it is stiff and strong. If the club head is made of the bulk-solidifying amorphous metal, it is stiff, strong, and hard, thereby resisting damage resulting from impact of the club head with the golf ball. In both components, the amorphous metal sustains very high levels of elastic deformation with essentially no plastic deformation. It has been demonstrated that elastic tensile strains of up to about 2 percent are achieved with essentially no anelastic or plastic response of the material. Accordingly, the large elastic strains sustained during impact of the club head with the ball are accompanied by essentially no anelastic or plastic response. Consequently, virtually no energy is absorbed during the deformation of the club head during impact with the golf ball. A higher fraction of the energy of the golfer""s swing is therefore transferred into the golf ball upon impact than in the case of the use of a material which exhibits a significant degree of absorption of energy by anelastic or plastic deformation.
The approach of the present invention also permits the weights of the different club heads in a club set to be varied independently of the volume of the club head or in conjunction with the volume of the club head in an arbitrary manner. The shapes and volumes of different club heads in a set vary. By custom and tradition, club weights increase from a 2-iron to a sand wedge. In the conventional approach, optimal design deals with the shape (i.e., volume) of the club head. The weights of the individual clubs cannot be varied outside of limits established either by professional standards or established user preferences. When conventional materials are used to make the club heads, the weights of the club heads vary directly proportionally to the volume of the club head.
According to the present invention, a set of golf clubs comprises a first club having a first club head with a first volume and made of a first bulk-solidifying amorphous alloy having a first composition and a first density. The set further comprises a second club having a second club head with a second volume and made of a second bulk-solidifying amorphous alloy having a second composition different from the first composition and a second density different from the first density. The first and second bulk-solidifying amorphous alloys are preferably selected from the same alloy family, i.e., alloys whose compositions are within the same continuous range.
The compositions and densities within a bulk-solidifying amorphous alloy system may be varied in small increments but over a wide range, permitting the weights of the club heads to be arbitrarily determined by composition selection within a wide range. An example is useful in illustrating this point. If it were desired that the club heads of two different clubs should have the same weight, a first product of the first volume times the first density, the weight of the first club head, is made about the same as a second product of the second volume times the second density, the weight of the second club head. That is, for this constant-weight situation the compositions of the alloys used to make the club heads are selected so as to vary their densities inversely with the volume of the club heads for which they are to be used. Known bulk-solidifying amorphous alloy families permit such density variation within the range of feasible club head design variations. The same principles are applied for the other clubs in the set. The golfer thus has a club set where the heads are of substantially constant weight, while also enjoying the other advantages of the bulk-solidifying amorphous alloys.
The constant-weight example is just one case of the ability provided by the present invention to arbitrarily vary the club-head weights independently of the club-head volume. The weights of the club heads of the set may instead be made to vary in some other fashion, independently of the club volume. This capability permits the club designer wide latitude in selecting club-head shapes and weights. The wide range of weights and tailoring of the weights are achieved with a homogeneous alloy material, and without the use of cumbersome weights, plugs, or other inserts that alter the impact and mass-distribution properties of the club head.
Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The scope of the invention is not, however, limited to this preferred embodiment.